Kad imam previše stresa, spavanje mi je važnije od filma.

Yes. Kad and kada both mean when.

• Kad is shorter and very common in everyday speech.
• Kada is a bit more formal or emphatic.

So in this sentence, Kad imam previše stresa... means When I have too much stress...

Both are correct:

• Kad imam previše stresa...
• Kada imam previše stresa...

Imam is the 1st person singular present tense of imati (to have).

So:

• imam = I have

The subject ja (I) is not stated because Croatian usually leaves subject pronouns out when the verb already shows who the subject is.

So:

• imam already clearly means I have
• You could say Kad ja imam previše stresa..., but ja is usually unnecessary unless you want emphasis.

Because previše (too much, too many) is normally followed by the genitive in Croatian.

So:

• stres = nominative
• stresa = genitive singular

That is why you get:

• previše stresa = too much stress

This is very common in Croatian. Similar patterns:

• puno posla = a lot of work
• mnogo vremena = a lot of time
• previše buke = too much noise

Spavanje is a verbal noun, often translated as sleeping or sleep.

It comes from the verb spavati (to sleep), but here it functions as a noun, not as a finite verb.

So:

• spavati = to sleep
• spavam = I sleep / I am sleeping
• spavanje = sleeping / sleep

In this sentence, spavanje is the thing being compared to film:

• Spavanje mi je važnije od filma.
• Sleeping is more important to me than a movie.

Using spavam would not work in the same structure, because the sentence needs a noun-like subject.

Mi here is the dative form of ja (to me / for me).

So:

• mi = to me

In the sentence:

• spavanje mi je važnije od filma

the literal structure is something like:

• sleeping is more important to me than a movie

In natural English, we often just say:

• sleeping is more important to me than watching a movie or
• sleep is more important to me than a movie

Croatian often uses this dative pronoun to show whose perspective or preference is involved.

Compare:

• To mi je važno. = That is important to me.
• Odmor mi je važniji. = Rest is more important to me.

Važnije is the comparative form of važno / važan (important).

Basic idea:

• važno = important
• važnije = more important

In this sentence:

• spavanje mi je važnije od filma = sleeping is more important to me than a movie

A useful pattern is:

• X je važniji / važnija / važnije od Y
  = X is more important than Y

Why važnije specifically? Because spavanje is a neuter singular noun, and the predicate adjective matches that.

So:

• film je važniji (masculine)
• knjiga je važnija (feminine)
• spavanje je važnije (neuter)

Od often means from, but after a comparative it means than.

So:

• važnije od filma = more important than a movie

After od in this kind of comparison, Croatian uses the genitive.

That is why:

• film = nominative
• filma = genitive

Other examples:

• bolji od mene = better than me
• veći od kuće = bigger than the house
• važniji od posla = more important than work

The sentence is slightly condensed. Croatian often compares broad ideas using a simple noun phrase.

So:

• spavanje mi je važnije od filma

literally compares sleeping and movie.

In natural English, the fuller idea may be:

• sleeping is more important to me than a movie
• sleeping is more important to me than watching a movie

If you wanted to make the second idea more explicit in Croatian, you could say:

• Spavanje mi je važnije od gledanja filma. = Sleeping is more important to me than watching a movie.

So the original sentence is natural, just slightly more compact.

Je is the 3rd person singular present of biti (to be).

Here it links the subject and the description:

• spavanje = subject
• je = is
• važnije = more important

So:

• Spavanje mi je važnije od filma. = Sleeping is more important to me than a movie.

Even though spavanje is neuter singular, Croatian still uses je because that is simply the 3rd person singular form of to be.

Croatian word order is more flexible than English word order.

All of these can be possible, depending on emphasis:

• Spavanje mi je važnije od filma.
• Mi je spavanje važnije od filma. (less neutral as a starting point)
• Spavanje je mi važnije... (not correct, because clitics like *mi and je have special placement rules)*

The important point is that mi and je are clitics, and Croatian clitics usually appear near the beginning of a clause, often in second position.

That is why mi je comes early:

• Spavanje mi je važnije od filma.

This is a very normal and natural order.

Here it is treated like an uncountable noun, much like English stress.

So:

• previše stresa = too much stress

You would normally not count it in this context.

Croatian can use plural forms of stres in some contexts, but in everyday usage for the general feeling or condition, singular is the normal choice:

• Imam puno stresa. = I have a lot of stress.
• Previše stresa mi šteti. = Too much stress harms me.

Sometimes yes, but the meaning shifts a little.

• spavanje = sleeping, the activity/process
• san = sleep, often as a state or amount of sleep

So:

• Spavanje mi je važnije od filma.
  focuses on the act of sleeping
• San mi je važniji od filma.
  sounds more like sleep/rest is more important to me than a movie

Both can work, but spavanje emphasizes the activity more clearly.

Not very naturally. A word-for-word version would be something like:

• When I have too much stress, sleeping to me is more important than a movie.

That is understandable, but not natural English.

A more natural English rendering would be:

• When I’m too stressed, sleep is more important to me than a movie.
• When I have too much stress, sleeping is more important to me than watching a movie.

So the Croatian structure is straightforward, but English usually adjusts it a bit to sound natural.